Fluke 27 Service Manual

Maintenance
Troubleshooting
3
3-17
XWWarning
The following procedure requires that high voltages be
supplied to the UUT for calibration. Read the safety precautions
in the Fluke 27 Users Manual before performing the following
procedure.
1. Select the ac voltage function (G) on the UUT.
2. Connect the DMM Calibrator to the volts/ohms/diode-test input terminal on the
UUT.
3. Program the DMM Calibrator output for 2.7 V ac at 100 Hz.
4. Adjust R7 to obtain a display of 2.700 V ac ±0.001 V ac.
5. Program the DMM Calibrator output for 270 V ac at 10 kHz.
6. Adjust C4 to obtain a display of 270.0V ac ±0.1 V ac.
7. Program the DMM Calibrator output for 1000 V ac at 10 kHz.
8. Adjust C10 to obtain a display of 1000 V ac ±1 V ac.
9. Program the DMM Calibrator output for 27.00 V ac at 10 kHz.
10. Adjust C8 to obtain a display of 27.00 V±0.01 V ac.
11. Program the DMM Calibrator output for 2.700 V ac at 10 kHz.
12. Adjust C6 to obtain a display of 2.700 V ac ±0.001 V ac.
13. Program the DMM Calibrator output for 2.700 ac at 100 Hz.
14. Verify that the UUT display indicates 2.700 V ac ±0.017 V ac.
15. Switch off both the DMM Calibrator and the UUT. Disconnect the DMM Calibrator
from the UUT.
16. Refer to the instructions in paragraph 30-10 to reassemble the UUT after calibration.
3-22. Troubleshooting
Caution
Static discharge can damage CMOS components U1 and U2.
Follow the handling precautions for static sensitive
components given previously. Never remove or install
components without first disconnecting all inputs to the
instrument and turning the function selector switch to OFF.
Refer to Table 3-4 and to the schematics in Chapter 5 of this manual as necessary during
the following troubleshooting procedures.
3-23. Power-Up Self Test
When the function switch is moved to any position from the OFF position, the
instrument performs a power-on self test. All LCD segments are switched on while the
test is being performed (about 1 second), then the unit commences normal operation.
3-24. Overall System Check
If the LCD display segments do not light, or if other malfunction indications occur
during power-up or operation, perform the following overall system check.. All
measurements are taken with respect to common. The overall system check is helpful in

Fluke 27 Specifications

General

Display Type	LCD
AC Voltage Range	0.1 mV to 1000 V
DC Voltage Range	0.1 mV to 1000 V
AC Current Range	0.1 μA to 10 A
DC Current Range	0.1 μA to 10 A
Battery Type	9V
Continuity	Yes
Diode Test	Yes
Safety Rating	CAT III 600V
AC Current Accuracy	±(1.5% + 2 digits)
Resistance Accuracy	±(0.2% + 1 digit)
DC Voltage Accuracy	±(0.1% + 1 digit)